Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

8. Elimination Reactions

SN1 SN2 E1 E2 Chart (Big Daddy Flowchart)

Organic Chemistry

8. Elimination Reactions

SN1 SN2 E1 E2 Chart (Big Daddy Flowchart)

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4:39 minutes

Problem 25a

Textbook Question

For each reaction, decide whether substitution or elimination (or both) is possible, and predict the products you expect. Label the major products.
a. 1−bromo−1−methylcyclohexane + NaOH in acetone

Verified step by step guidance

Analyze the structure of the starting material: The compound is 1-chloro-1-methylcyclohexane, which is a secondary alkyl halide due to the carbon attached to the chlorine being bonded to two other carbons.

Identify the reagent: tert-BuO⁻Na⁺ (sodium tert-butoxide) is a strong, bulky base. Bulky bases favor elimination (E2 mechanism) over substitution because steric hindrance makes it difficult for the base to approach the carbon for substitution.

Determine the reaction mechanism: Since the base is strong and bulky, the reaction will proceed via the E2 elimination mechanism. In this mechanism, a β-hydrogen (hydrogen on a carbon adjacent to the carbon bearing the leaving group) is abstracted, and the leaving group (Cl⁻) departs simultaneously, forming a double bond.

Predict the product: The β-hydrogens are located on the carbons adjacent to the carbon bearing the chlorine. Elimination can occur to form a double bond between the α-carbon (the carbon with the chlorine) and one of the β-carbons. Due to steric hindrance, the major product will be the less substituted alkene (Hofmann product), as the bulky base prefers to abstract the less hindered β-hydrogen.

Label the major product: The major product will be 1-methylcyclohexene, as it is the less substituted alkene. The minor product, if formed, would be 1,2-dimethylcyclohexene (the more substituted alkene, Zaitsev product).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Substitution Reactions

Substitution reactions involve the replacement of one functional group in a molecule with another. In organic chemistry, this often occurs with alkyl halides, where a nucleophile attacks the carbon atom bonded to the halogen, leading to the formation of a new bond and the release of the halide ion. The two main types of substitution reactions are SN1 and SN2, which differ in their mechanisms and kinetics.

Elimination Reactions

Elimination reactions involve the removal of a small molecule, typically a halide and a hydrogen atom, from adjacent carbon atoms, resulting in the formation of a double bond. These reactions can be classified as E1 or E2, depending on whether they proceed through a carbocation intermediate or a concerted mechanism. The choice between substitution and elimination often depends on the structure of the substrate and the reaction conditions.

Reaction Conditions and Solvent Effects

The choice of solvent and reaction conditions significantly influences whether a substitution or elimination reaction predominates. Polar protic solvents favor SN1 and E1 mechanisms by stabilizing carbocations, while polar aprotic solvents favor SN2 and E2 mechanisms by enhancing nucleophilicity. In this case, the use of acetone, a polar aprotic solvent, suggests that elimination may be favored, especially with a strong base like NaOH.

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Related Practice

Textbook Question

Write a balanced equation for each reaction, showing the major product you expect.

(d)

Textbook Question

Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely.

h. 1-bromo-1-methylcyclopentane heated in methanol

Textbook Question

Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely.

g. 1−bromo−1−methylcyclopentane + NaOEt in ethanol

Textbook Question

Predict the major and minor elimination products of the following proposed reactions (ignoring any possible substitutions for now). In each case, explain whether you expect the mechanism of the elimination to be E1 or E2.

(a)

Textbook Question

Under second-order conditions (strong base/nucleophile), S_N2 and E2 reactions may occur simultaneously and compete with each other. Show what products might be expected from the reaction of 2-bromo-3-methylbutane (a moderately hindered 2° alkyl halide) with sodium ethoxide.

Textbook Question

When (1-bromoethyl)cyclohexane is heated in methanol for an extended period of time, five products result: two ethers and three alkenes. Predict the products of this reaction, and propose mechanisms for their formation.

Textbook Question

Give the substitution and elimination products you would expect from the following reactions.

a. 3-bromo-3-ethylpentane heated in methanol

Textbook Question

Write a balanced equation for each reaction, showing the major product you expect.

(b)

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For each reaction, decide whether substitution or elimination (or both) is possible, and predict the products you expect. Label the major products. a. 1−bromo−1−methylcyclohexane + NaOH in acetone

Key Concepts

Substitution Reactions

Elimination Reactions

Reaction Conditions and Solvent Effects

Watch next

For each reaction, decide whether substitution or elimination (or both) is possible, and predict the products you expect. Label the major products.
a. 1−bromo−1−methylcyclohexane + NaOH in acetone